1. Technical Field of the Invention
The present invention relates generally to a gas sensor which may be employed in an air-fuel ratio control system for automotive vehicles for measuring the concentration of gas such O.sub.2, NOx, or CO, and more particularly to an improved structure of such a gas sensor which provides for ease of installation of a protective cover on a cover mount, firm engagement of the protective cover with the cover mount, and ease of machining of the cover mount.
2. Background Art
Typical gas sensors employed in measuring the concentration of O.sub.2, NOx, or CO in exhaust gasses of an internal combustion engine include a gas sensitive element, a sensor mount, and a protective cover. The sensor mount is used in mounting the sensor in an exhaust pipe and also serves as a holder which retains therein the gas sensitive element. The protective cover is installed on the sensor mount so as to cover the gas sensitive element. The gas sensors usually undergo a temperature change from room temperature to approximately 1000.degree. C. after the engine is started, thereby causing thermal stress to be produced between the sensor mount and the protective cover, which may result in dislodgment of the protective cover from the sensor mount.